JPH05235057A - Semiconductor device - Google Patents

Abstract

PURPOSE:To realize a function other than an operation like a three-pole vacuum tube by semiconductor device which utilizes a tunnel effect. CONSTITUTION:A GaAs quantum well layer held between barrier layers consisting of an AlAs layer having an electron affinity smaller than that of a GaAs layer is provided between respective ohmic contacts (GaAs layers) of a source 2 and a drain 3. Only when the quantum well layer and the ohmic contact of the source 2 are brought in a resonance state, the source and a channel are connected to each other, a tunnel junction is formed between the source and the drain and a drain current flows. As a result, negative resistance is shown at a voltage region in a state exceeding the resonance state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field effect semiconductor device which controls a drain current by a tunnel effect.

[0002]

2. Description of the Related Art A surface tunnel transistor has been proposed as a quantum effect device of a new principle suitable for miniaturization ("Proposal and Prototype of Surface Tunnel Transistor" p.116).
0, Toshio Baba; Basic Research Laboratories, NEC Corporation: Autumn Meeting, Japan Society of Applied Physics 9a-K-2). FIG. 1 is a schematic cross-sectional view showing the structure of the surface tunnel transistor described above. The GaAs substrate 1 has a source 2 having an ohmic contact of n ⁺ -GaAs and a conductivity type different from that of the source 2 and a high impurity concentration. A drain 3 having ohmic contact with p ⁺ -GaAs, which is a degenerate semiconductor included in the concentration, is formed, and an Al gate electrode 5 is connected between the source 2 and the drain 3 via an AlGaAs insulating layer 4.

Next, the operation will be described. Reverse bias is applied between the source and drain. When the gate voltage is made positive and electrons are accumulated in the channel under the gate, the source and the channel are connected and a tunnel junction is formed between the channel and the drain. Therefore, a drain current (tunnel current) flows through the tunnel junction depending on the gate voltage, and the transistor exhibits non-saturation characteristics like a triode vacuum tube.

[0004]

The surface tunnel transistor described above operates as a triode vacuum tube by controlling the drain current by utilizing the tunnel effect, but has no other function.

The present invention has been made to solve the above problems, and a semiconductor device in which the drain current is controlled by utilizing the tunnel effect has a function other than a triode vacuum tube operation. The purpose is to provide a device.

[0006]

A semiconductor device according to the present invention has a channel layer between a source region made of a first semiconductor of one conductivity type and a drain region made of a first semiconductor of another conductivity type, In a semiconductor device in which a gate electrode is connected to a channel layer via a second semiconductor having an electron affinity lower than that of the first semiconductor, the channel layer has an electron affinity higher than that of the first semiconductor in the direction from the source region to the drain region. It is characterized in that a small barrier layer made of a third semiconductor, a quantum well layer made of a first semiconductor, and a barrier layer made of a third semiconductor are formed in this order.

[0007]

In the semiconductor device according to the present invention, the channel and source are connected only when the quantum well layer and the ohmic contact of the source are in a resonant tunnel state due to the voltage applied across the quantum well layer, and the source and source are connected. A tunnel junction is formed between the drains and current flows, but when the resonance tunnel state is exceeded, the barrier layer prevents the formation of a tunnel junction.
It shows a negative resistance in which the drain current decreases with increasing voltage.

[0008]

The present invention will be described below with reference to the drawings showing the embodiments thereof. FIG. 2 is a schematic sectional view showing the structure of the field effect transistor according to the present invention. n ⁺ -GaAs substrate 1 has n ⁺ -GaAs (n = 6 × 10 ¹⁸ cm ^-3 , 250 nm) as ohmic contact source 2 and has a smaller electron affinity than GaAs.
Barrier layer of doped AlAs (5 nm), quantum well layer of undoped GaAs
(5nm), undoped AlAs barrier layer (5nm) and undoped GaAs
P ⁺ -GaAs (p = 5 × 10 ¹⁹ cm ^-3 , 10) which is a conduction type different from the layer (190 nm) and source 2 and contains a high concentration of impurities
The drain 3 having an ohmic contact of 0 nm) is laterally grown in this order, and the AlGaAs insulating layer 4 (having a smaller electron affinity than GaAs) regrown between the source 2 and the drain 3 after the mesa structure is formed. An Al gate electrode 5 and AuGe / Au source / drain electrodes are formed via 100 nm).

The widths of the barrier layer and the quantum well layer described above are set so that electron waves can be transmitted by the tunnel effect.

Next, the operation will be described. A reverse bias is applied between the source and drain. When the gate voltage is positive, electrons are accumulated in the channel under the gate, and the quantum well layer (GaAs) is connected to the ohmic contact (n ⁺ -G) of the source 2.
The source-channel is connected and a large current flows between the channel-drain only when it enters a resonance tunnel state with (aAs).

However, when the resonance tunnel state is exceeded, the drain current decreases and the drain current decreases. When the drain voltage further increases, a normal diffusion current flows. The negative resistance characteristic of the field effect transistor according to the present invention was confirmed at 77K.

Due to the above negative resistance characteristics, amplification
Functions such as oscillation can be realized.

[0013]

As described above, since the semiconductor device according to the present invention exhibits a negative resistance, it has an excellent effect of realizing a function other than a triode vacuum tube operation.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a conventional surface tunnel transistor.

FIG. 2 is a schematic sectional view of a field effect transistor according to the present invention.

[Explanation of symbols]

 2 source 3 drain 5 gate electrode 7 channel layer

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Claims (1)

[Claims] 1. A channel layer is provided between a source region made of one conductivity type first semiconductor and a drain region made of another conductivity type first semiconductor, and the channel layer has an electron affinity higher than that of the first semiconductor. In a semiconductor device in which a gate electrode is connected via a small second semiconductor, a barrier layer made of a third semiconductor having an electron affinity smaller than that of the first semiconductor in a direction from a source region to a drain region in a channel layer, 2. A semiconductor device having a quantum well layer made of the above semiconductor and a barrier layer made of a third semiconductor in this order.